Security services in Norway and elsewhere in the region had recently shifted their focus to Islamist extremism, letting other forms of terror slip under the radar, experts said.
While there had been initial fears that Friday's twin attacks might have been an act of revenge for Norway's participation in the campaigns in Afghanistan and Libya, everything changed when it emerged the suspect was a native Norwegian.
Named by media as Anders Behring Breivik, the alleged killer has been described by police as a "fundamentalist Christian" whose political opinions leaned "to the right." He had also been a member of the populist right-wing Progress Party (FrP) and was a member of a Swedish neo-Nazi Internet forum.
For some, the suspect is an example of far-right extremism, which has got less attention while intelligence agencies concentrated on radical Islam.
For others, such as Daniel Poohl of Sweden's Expo foundation, a leading group in monitoring far-right activity across Scandinavia, he is representative of a new kind of terrorism fuelled by anti-Muslim sentiment.
The manifesto Behring Breivik posted online showed his act was prompted by a hatred of Islam, Poohl told AFP, and in that respect he differs from extremists in violent far-right groups.
In a report published earlier this year, Norway's intelligence agency said that far-right extremists existed in Norway, but that they had "barely been active in recent years."
"However, the trend that saw an increased level of activity in 2010 is expected to continue in 2011," the Norwegian Police Security Service (PST)'s annual threat assessment report read.
But the PST noted that "as in previous years, the far-right and far-left extremist communities will not represent a serious threat to Norwegian society in 2011."
"The lack of strong leadership limits the growth of these groups," it said.
Instead, it said it was "primarily" Islamist extremists "who could pose a direct threat to Norway in the year ahead."
Robert Oerell of Sweden's Exit foundation, which helps those who wish to leave nationalist, racist and Nazi-oriented groups and movements, said that the focus on Islamist radicals had favoured far-right extremists.
"It justifies their perception that the Nordic people are under threat from Islamists," he told news agency TT.
Matthew Goodwin, a lecturer at the University of Nottingham in England and an expert on far-right groups, agreed that the focus on Islamist extremism had let other extremists go neglected.
"For the past decade our (British) security services have been heavily geared towards Al-Qaeda and Northern Ireland, which has left a real gap in their coverage of the far-right," he told AFP.
"Scandinavian countries have also been involved in Afghanistan and Iraq and their security services have the same problem," he said.
Oerell said he was surprised by the twin bomb and gun attacks, which killed at least 92 people, including 85 shot dead at a summer youth camp organised by the ruling Labour Party.
"My understanding of the Norwegian movements is that they are not as organised or large as the Swedish ones, which have more capacity for violence, so from that point of view I am surprised," he told AFP.
"On the other hand, I am not surprised that, according to the information I have, a single person acted on their own, and then we can recall Timothy McVeigh case, whose example has mobilised such people in the extreme right movements before," he said.
"Timothy McVeigh is still seen by some groups in the US as a hero," agreed Goodwin.
"As soon as I heard about Norway I thought this would be the far-right, so on that level it is not a surprise. I would not necessarily say it was brewing but we have seen a few trends pointing towards it," he told AFP.
Expo said Saturday Behring Breivik was a member of a 22,000-strong Swedish Nazi Internet forum called Nordisk.
The forum includes posts inciting to violence and threads on the Turner Diaries, a 1978 novel about a violent revolution in the United States which inspired McVeigh's 1995 Oklahoma City bombing, according to Expo.
Discussions on the site website are "often of a racist nature," Expo said, and range "from everything from white power music to political strategies to crush democracy," Expo said.
The attacks on Friday afternoon were western Europe's deadliest since the 2004 Madrid bombings, carried out by Al-Qaeda.